1. Field of the Invention
This invention generally relates to an automatic icemaker, and more specifically to an improved icemaker for creating ice cubes in a user selectable continuum of qualities which may be judged to be between either “fast” in freezing rate or “clear” in appearance, or some combination thereof.
2. Description of the Related Art
The typical icemaker found in the kitchen refrigerator is located in the freezer section of the appliance. In its simplest form, water is introduced into a mold, frozen, and then harvested into a container positioned beneath the mold. In more complicated systems, ice is made in a mold, harvested into a bucket, transported to a delivery or exit port using a motorized auger, crushed or left intact, and delivered on demand to a drinking vessel or other container held by the user.
Ice making can be regarded as a three part process. In the first part of the process, sensible heat is removed from water which has been directed into the mold, until the water is nearly at its freezing temperature of 32° F. The term “sensible heat” has the same meaning as “enthalpy”; namely the heat absorbed or transmitted by a substance during a change of temperature which is not accompanied by a change of state.
The second part is the ice making process, additional heat (usually called the latent heat of fusion—144 BTU/lb) is removed from the water as it changes state from 32° F. water to 32° F. ice. In the third part of the process, the remaining sensible heat is removed and the 32° F. ice is further cooled to harvest temperature (often below 32° F. to perhaps as low as 0° F.) for delivery to the awaiting ice bin, bucket or suitable container.
To reduce the time it takes to freeze water to ice which can be harvested, refrigeration engineers incorporate design features in the ice making system that direct the highest volume of the coldest air (available in the freezer section of the kitchen refrigerator) into the icemaker cube mold area. Water in the ice cube mold is frozen as quickly as possible, harvested to the bucket or container, and the mold automatically refilled with water. This sequence of freeze-harvest-refill events results in the most “pounds per hour” of ice possible; however, rapid freezing directly contributes to the creation of cloudy ice.
Cloudy ice forms for a number of reasons, but perhaps the most significant is because impurities in the source water are entrained in the rapidly freezing ice-front present in the cube. This is because the typical water freezing rate exceeds the diffusion rate of the impurities in the water (typically dissolved gases such as nitrogen or carbon dioxide) and the freeze front direction is not well controlled.
In-line carbon block water filters typically supplied with automatic icemakers remove particulates and improve taste and odor of water caused by chlorine. However, these filters are not capable of removing significant amounts of dissolved gas, nor are fluid metering systems able to control the amount of gas re-dissolved into the mold water during the simple act of refilling.
Slow freezing usually creates clear ice, but typically available water spray or freezing tube clear ice systems are available only as commercial icemakers and are not suitable for general residential home use due to higher initial costs, higher installation costs and higher maintenance costs. Perhaps more importantly, there is a consumer need for ice which meets the occasion of its use—if ice for a portable picnic cooler is needed, the clearest possible ice is usually not necessary—nor is the cloudy, fast ice acceptable for a scheduled evening cocktail party.
To create ice cubes of a quality that better meets consumer requirements, the most important part of the ice making system needing improvement is the mold and associated design elements—referred to from this point on as the icemaker. Once ice is created that meets the quality expectations of the consumer, ice cube storage and ice cube delivery can be addressed in a number of ways.